10/09/2025 CONSERVATION COMMISSION Minutes

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Town of Mashpee Conservation Commission 16 Great Neck Road North Mashpee, MA 02649 barriers. The team is currently working with the Department of Conservation and Recreation (DCR) to detennine the most appropriate permitting route and will update the Commission once guidance is finalized. Questions from Commissioners The Chair invited questions from the Commission. Vice Chair Thornbrugh began by commending Ms. Tyrell for her"wonderful"presentation and asked for clarification about whether Doghead Marsh is entirely surrounded by open space, Fish and Wildlife property, and conservation land, or if it borders any developed areas. Ms. Tyrell confirmed that Doghead Marsh is fully surrounded by state or town-owned land, while Jehu Pond has some federal ownership. She elaborated that marsh restoration specialist Wendy Ferguson from Save the Bay—credited with pioneering the runneling technique on the East Coast—had recommended relocating a trail at Doghead Marsh to accommodate inland marsh migration. WBNERR is working on that adjustment. While Doghead Marsh faces long-term challenges from an undersized culvert and sedimentation issues, Ms. Tyrell said these are future considerations, not immediate project elements. Assistant Conservation Agent Kent, noted that any proposed trail relocation would eventually come before the Commission for review. Ms. Tyrell acknowledged that her colleague, Ryan, would likely lead that portion when the time comes. Thin-Layer Placement and Additional Restoration Tools Conservation Agent McManus then asked about previous "thin-layer placement" efforts—where sediment is spread across the marsh surface to raise elevation—and whether that method would be used in conjunction with runneling. Ms. Tyrell said that experimental-scale thin-layer placement was done on the north side of Sage Lot Pond, yielding good revegetation results. Interestingly, even untreated areas nearby also revegetated, which she attributed to favorable timing within the natural 18.6-year metonic tidal cycle that alternates between higher and lower tides. She expressed interest in expanding beneficial reuse of clean dredged material,particularly sandy sediments, for marsh elevation enhancement. She mentioned awareness of related projects in the Great River and Little River areas and her willingness to coordinate future efforts. Ms. Tyrell emphasized that runneling is only one tool among several potential restoration strategies. While sediment augmentation would be ideal for some sites, the current focus remains on low-impact hydrological interventions, with an eye toward more complex methods in the future as conditions and resources allow. Impact of Burrowing Crabs As the discussion closed, Ms. Tyrell added that she had neglected to mention one important factor affecting marsh health: the burrowing crab Sesarma reticulatum, which feeds on aboveground vegetation and undermines marsh stability. She said her final slides included examples showing how these crabs have altered monitoring plots over recent years, underscoring another ecological challenge for salt marsh restoration. Discussion of the Purple Marsh Crab and Its Impact Ms. Tyrell discussed an emerging ecological concern affecting Mashpee's salt marshes the purple marsh crab (Sesarma reticulatum). She displayed images showing creek banks that have become denuded and severely eroded due to the burrowing and feeding activity of these crabs. She explained that what should be an intact peat platform is instead breaking down into pinnacled, unstable formations. The crab's behavior and its rapid expansion are well-documented along the East Coast, and it has been shown to cause salt marsh dieback by consuming both above-ground vegetation and the underlying roots. Ms. Tyrell noted that,paradoxically, runneling a restoration technique used to improve marsh hydrology can inadvertently create small ditches that serve as ideal habitats for the crabs, thus requiring careful monitoring. She first observed signs of this species locally in 2023 and recognized it immediately, as she had